Field of the Invention
The invention relates to pharmaceutical active substances, active substance mixtures and formulations for use as an aerosol in propellant-containing [1.1.1.2-tetrafluoroethane (HFC-134a) or 1.1.1.2.3.3.3-heptafluoropropane(HFC-227)] metered-dose aerosols and the metered-dose aerosols for administering these active substances, active substance mixtures and formulations.
Description of the Prior Art
The use of the delivery of aerosol formulations of medicaments by pressurised, dosage-measuring inhalers (MDIs, standing for “metered-dose inhalers”) is widespread in therapy, as in the treatment of asthma and diseases that cause obstruction of the airways. Compared with oral administration, inhalation results a faster onset of activity and at the same time reduces systemic side-effects to a minimum. Aerosol formulations can be administered by inhalation through the mouth or topically by application to the nasal mucosa.
Formulations for administering aerosol using MDIs may consist of solutions or suspensions. Solution formulations have the advantage over suspension formulations that the pharmaceutical compositions are fully dissolved in the propellant and thus have a homogeneous nature. Solution formulations also avoid the problems associated with suspension formulations of physical instability and thus ensure the administration of equal doses for a longer period. In addition, solution-type metered-dose aerosols generally do not require the addition of surfactants. Moreover, there are so-called “suslutions” as disclosed in US2004/0184994 for example.
The administration of aerosol solution formulations by MDIs is dependent on the propellant force of the propulsion system used to produce them.
Conventionally, the propellant contains a mixture of chlorofluorocarbons (CFCs) to guarantee the desired properties of solubility, vapour pressure and stability of the formulation. However, as it has been established in the mean time that CFCs are damaging to the environment because they contribute to the depletion of the earth's ozone layer, the environmentally harmful CFC propellant present in aerosol inhalation formulations is being replaced by environmentally acceptable partly fluorinated hydrocarbon propellants (HFC propellants) or other non-chlorinated propellants.
Although there are a great many metered-dose aerosols on the market, their metering accuracy is suitable for improvement.